Ya that will have to be done at a body shop, they would pop out the dents as best as they could a then bondo over it and smooth it out then paint it. Unless you know yourself how to do body work but doubt it since you asked.

Getting a new rear quater panel would be very pricey, if you did that they would have to cut out that area and weld on a piece of that quater panel you bought and then smooth out the welds and paint.